# Atomic Layer Processes for UV-Stable Polymers: Synergistic Effects of Infiltration and Deposition of ZnO

## TL;DR

This paper introduces a new method to make UV-resistant polymers by combining two techniques to create a protective ZnO coating, improving durability and reducing plastic waste.

## Contribution

A synergistic combination of VPI and ALD to create conformal ZnO films on UV-sensitive polymers, significantly enhancing UV stability.

## Key findings

- Sequential VPI and ALD application increases ZnO growth per cycle by over 10-fold.
- ZnO–PLA hybrids absorb over 90% of UV–C radiation while remaining optically transparent.
- The method is scalable and suitable for 3D-printed and thin-film polymer structures.

## Abstract

Ultraviolet (UV) radiation is the major cause of polymer
degradation
in outdoor environments, accelerating mechanical failure and color
change, leading to plastic waste accumulation. Effective UV-protective
strategies that preserve polymer functionality are therefore critical
for extending material longevity in UV-intense environments. Here,
we present a synergistic approach combining vapor phase infiltration
(VPI) and atomic layer deposition (ALD) to engineer nanoscale zinc
oxide (ZnO) coatings on poly­(lactic acid) (PLA), a UV-sensitive polymer.
Individually, ALD and VPI offer minimal enhancement in UV stability;
however, their sequential application enables the formation of conformal,
polycrystalline ZnO films that dramatically improve UV resistance
in both 3D-printed structures and thin-film PLA models. In situ microgravimetry
and cross-sectional electron microscopy reveal that VPI introduces
ZnO nucleation sites within and atop the polymer matrix, promoting
a >10-fold increase in ZnO growth per ALD cycle. The resulting
ZnO–PLA
hybrids absorb over 90% of incident UV–C radiation while maintaining
high optical transparency in the visible range. This low-temperature,
scalable process provides a promising platform for the development
of transparent, durable UV-barrier coatings on polymers for use in
environmentally demanding applications.